A liquid crystal display device or an organic electroluminescence display device (described as an EL display device hereinafter) includes a plurality of pixels including a display element such as a liquid crystal element and a light emitting element, it is possible to provide an image by controlling the driving of each pixel.
A display device is manufactured by stacking an insulating film, a semiconductor film and a conductive film, and shaping these thin films into a certain shape. Specifically, each transistor and each circuit in the display device which are formed by a transistor, a wiring pattern forming each circuit, and a wiring pattern routed from a terminal part to which an image signal, a timing signal for controlling the operation of a circuit, and a power supply voltage or the like is applied are manufactured.
In recent years, display devices have been increasing in size and higher definition. Despite the progress in the size of display devices and higher definition, a low resistance material is used for wiring in order to prevent delay of a signal for driving the display device and a voltage drop of a power supply. The low resistance material is aluminum (Al) for example.
On the other hand, aluminum (Al) causes display defects such as a bright spot on the display device due to the treatment in the process of forming the wiring, which lowers the display yield. In order to suppress a decrease in display yield, for example, Japanese Laid Open Patent Publication No. 2011-151194 discloses using a multilayer wiring structure including titanium (Ti) on a lower layer and an upper layer of aluminum (Al).